FIELD OF THE INVENTION
[0001] The present invention relates to sports timing. More particularly, the invention
relates to sports timing detection elements and a sports timing system comprising
the detection elements based on backscattering modulation.
BACKGROUND
[0002] Radio Frequency Identification (RFID) tags are widely used in automatic time registration
systems in sporting events. Typically an RFID tag comprises a microchip combined with
an antenna and is structured to allow attachment to an object to be detected. In such
time registration systems every participant of a sporting event is provided with an
RFID tag, which is removable secured to e.g. a shoe or a bib comprising a number,
which is associated with the name and/or address of the participant. If a participant
crosses a detection antenna an electro-magnetical coupling between the tag and the
detection antenna is established thereby allowing information exchange, e.g. an identify
number associated with the tag, between the tag and a detector connected to the detection
antenna.
[0003] Tags may be so-called ultra-high frequency (UHF) tags, which use frequency in the
UHF band between approximately 860 and 960 MHz. These tags are relatively cheap (so
that they can be used as a one-time use disposable tag), are relatively light-weighted,
and can be read faster and from larger distances when compared with low frequency
tags.
[0004] In sporting events such as bicycle races, marathons and triathlons a detection antenna
is typically implemented as a detection mat placed on the ground, such as shown in
Fig.7. Such detection mat 11,12,13 is typically connected to an RFID reader 10 at
the side of the track. The RFID tag 1 of the participant is detected when the participant
1 crosses the detection mat 12. Hereto a carrier signal 2 is transmitted by an antenna
in the detection mat 12 and in response thereto a backscatter signal 3 is transmitted
by the RFID tag 1 and detected by the antenna in the detection mat 12. The detection
antennas ideally cover the width of the track to enable detection of all participants
when crossing e.g. the start line or finish line. As a single detection mat has a
limited width, e.g. a width of 1 meter, multiple detection mats 11,12,13 are typically
placed in one or two parallel lines across the width of the track. In this configuration
the antenna mats 11,12,13 are connected to the RFID reader 10 via coax lines 14,15,16,
respectively.
[0005] Existing detection mats, such as used at start lines and finish lines of sporting
events, are typically remote antennas coupled to a central RFID reader via coax lines.
There are several disadvantages of such configuration.
[0006] Firstly, with each antenna mat being connected to the central RFID reader at the
side of the track, relatively long cables are needed to connect each antenna to the
reader, resulting in a signal loss (the longer the cable, the higher the signal loss).
[0007] Secondly, installation of the detection mats can be time consuming, while the available
installation time is typically limited. Installation can be time consuming because
each cable has to be carefully installed, such that participants cannot damage the
cables e.g. by stepping on it. Hereto the cables are typically installed in cable
ducts, possibly embedded in the detection mats. Installation time, on the other hand,
is often limited because public roads temporary used for a sporting event are to be
closed as late as possible.
[0008] Thirdly, because coax cables are rigid they are difficult to handle. One has to be
careful not to bend the cables beyond damaging point. Furthermore, coax cable connectors
are vulnerable to dirt and mechanical damages.
[0009] Fourthly, the maximum number of connected detection mats is typically limited (e.g.
to a maximum of eight) by the space occupied by the coax cables in the cable ducts.
[0010] US 20010/0265801 discloses a timing system having multiple detection mats placed on the ground, wherein
each antenna mat is connected to a control, detection and timing circuitry (i.e. including
the RFID reader) via a cable. The detection mats include conduits to accommodate the
cables coming from the detection mats. When installing the detection mats, the cables
have to be carefully placed into the conduits and connected to the RFID reader at
the side of the track. This task is time consuming and prone to incorrect connection
of one or more mats to the RFID reader.
[0011] There is a need for improved sports timing detection elements for detecting tags
in sporting events such as bicycle races, marathons and triathlons, which are easier
to install.
SUMMARY OF THE INVENTION
[0012] The present invention provides an improved sports timing detection element, particularly
suitable for use in sporting events such as bicycle races, marathons and triathlons.
The improved sports timing detection element may be implemented as a detection mat
for use on the ground, as a vertical detection element or as an overhead detection
element. Multiple detection elements are easily interconnectable to increase the detection
width of the detection elements, for example to cover the width of a track at a start
line or finish line.
[0013] According to a first aspect of the invention a sports timing detection element based
on backscattering modulation is proposed. The backscatter modulation is for example
based on RFID backscattering modulation in the UHF band. The detection element can
comprise at least one antenna, a receiver circuitry, a transmitter circuitry and a
microprocessor. The microprocessor can be configured to activate the transmitter circuitry
for transmitting a carrier signal via the at least one antenna. The microprocessor
can further be configured to process a backscatter signal received via the at least
one antenna and the receiver circuitry in response to the carrier signal. The detection
element can further comprise a data bus for exchanging data with a further detection
element.
[0014] The data bus enables the detection element to be easily connected to another detection
element. Because a data bus is used, there is no need to have individual cables from
each detection element, e.g. to an external controller device. Instead, the data busses
of the detection devices may be interconnected to create a single (i.e. serial) data
bus along the detection elements when interconnected. Another advantage of the data
bus is that the cables used for connecting the detection elements to for example the
external controller device need not be rigid and are less susceptible to external
damage. With the data busses interconnecting to form a single data bus when the detection
elements are connected, there is no need for having long cables from each detection
element to for example the external controller device.
[0015] The microprocessor in the detection element processes the backscatter signal. The
thus obtained data can be transmitted via the data bus to another detection element
or to an external controller device (possibly via another detection element). The
microprocessor is for example a processor running a computer program stored in a memory
(e.g. NVRAM or ROM). Another example of a microprocessor is a Field Programmable Gate
Array (FPGA) that is hardcoded with the computer program code.
[0016] An example of a data bus is a Controller Area Network (CAN) bus. Via the CAN bus
data may be exchanged between detection elements and between a detection element and
for example an external controller device. Another example of a data bus is a RS485
bus. The external controller device is for example a computer used for collecting
the data from the detection elements. This data, which is obtained by the microprocessor
in the detection element after processing the backscatter signal from a tag, typically
includes sports timing information of the participants of the sporting event. The
external controller may also be used to synchronize detection elements when interconnected,
e.g. by switching one or more interconnected detection elements on or off to reduce
interference between the detection elements. Such synchronization may alternatively
be achieved by having the detection elements exchange synchronization data directly,
i.e. without involving an external controller device.
[0017] Advantageously, by locally processing the backscatter signal, i.e. in the detection
element/detection mat, the distance between the antenna and the processor is relatively
short compared to the length of the coax cables between the antennas and the RFID
reader in Fig.7. Potential signal losses between the antenna and the processor are
thereby minimal. The detection element may have one or more connectors for interconnecting
the data bus of one detection element with the data bus of another detection element,
thereby forming a single data bus extending the interconnected detection elements.
The connectors may be located at a fixed location in a protective casing of the detection
element, the protective casing forming e.g. a detection mat. Making a connection between
the detection elements by connecting the connectors is straightforward and thus less
time consuming compared to e.g. the configuration of Fig.7 wherein cables have to
be installed. The data bus may be embedded in the detection element or its protective
casing such that, contrary to the installation of the coax cables in Fig.7, there
is a very low chance of damage during installation of the detection elements for a
sporting event.
[0018] In an embodiment the detection element further comprises a polarization switch to
switch the polarization of an antenna, such as between a horizontal polarization and
a vertical polarization or between a linear and a circular polarization.
[0019] Switching of the polarization enables better detection of backscatter signals with
tags being positioned differently on the participants. For example a tag that is positioned
horizontally on a bib worn on the chest can be optimally detected with a horizontally
polarized detection antenna in a detection mat placed on the ground. A vertically
positioned tag on a bib or participant can be optimally detected by a vertically polarized
detection antenna in a detection mat that is placed on the ground or vertically oriented
(i.e. allowing the participant to pass the antenna mat from the side). By enabling
the polarization to be switched, the detection element may be used in both setups,
and possibly others.
[0020] In an embodiment the detection element comprises a first antenna and a second antenna.
The detection element can be configured to transmit the carrier signal via the first
antenna and to receive the backscatter signal via the second antenna.
[0021] Separation of the transmitting and receiving via separate antenna results in a better
reception of the backscatter signal, because there is less interference between the
carrier signal and the backscatter signal with separated antennas.
[0022] In an embodiment the detection element further comprises a cross-over switch to switch
between the first antenna and the second antenna for transmitting the carrier signal.
[0023] This is for example useful when a detuning is detected on the transmitter antenna,
e.g. due to a participant standing or stepping on the transmitter antenna. By switching
to another antenna the detected detuning effect may be reduced or avoided, typically
because the chance that the participant is standing on both antennas at the same time
is low.
[0024] In an embodiment the detection element is configured to receive the backscatter signal
via the first antenna and the second antenna.
[0025] This can improve the detectability of the backscatter signal in the detection element
in case the strength of the backscatter signal is too low at one of the antennas to
be detected.
[0026] In an embodiment the detection element further comprises a comparator module configured
to compare a first reflection signal received via the first antenna with a second
reflection signal received via the second antenna to obtain a comparison result. The
microprocessor can be further configured to, based on the comparison result, switch
off one of the first antenna and the second antenna for transmitting the carrier signal.
The microprocessor can be further configured to, based on the comparison result, lower
a transmission power for transmitting the carrier signal via one of the first antenna
and the second antenna.
[0027] For example due to an antenna mismatch, a reflection of the carrier signal may be
detected on the antenna ports. This reflection is called a reflection signal. The
comparator is used to determine if the reflection signal is larger at one of the two
antennas. The comparison result may then be used to switch off the antenna with the
highest reflection signal. The first and second reflection signals may originate from
the same carrier signal.
[0028] If the power of the reflection signal is too large, the backscatter signal may not
be detectable. Lowering the transmission power for transmitting the carrier signal
may reduce or eliminate the reflection signal, enabling the backscatter signal to
be detectable again. The lowering of the transmission power may be a temporary measure.
[0029] In an embodiment the detection element further comprises a microcontroller that is
configured to determine an identity of the detection element.
[0030] The microcontroller is typically implemented as a small computer on a single integrated
circuit containing a processor core, a memory and programmable input/output peripherals.
The microprocessor may be a part of the microcontroller. The microprocessor and the
processor core of the microcontroller may be one and the same.
[0031] The microprocessor is typically configured to process the backscatter signal and
control the receiver antenna and transmitter antenna. The microcontroller typically
interfaces between the microprocessor and the data bus and is typically involved in
the communication with other detection elements and/or an external controller device.
The microcontroller can set, obtain, detect or otherwise determine the identity of
the detection element, which identity may be transmitted along with the data on the
data bus.
[0032] In an embodiment the data bus comprises one or more power lines. The microcontroller
can be configured to determine the identity based on a measurement result obtained
by measuring the one or more power lines.
[0033] A line is typically implemented as a copper conductor with isolating cover, e.g.
implemented on a circuit board or as a copper wire. The power lines can provide the
electronics of the detection element with power. The power may originate from an external
controller device or any other external power source that is connected to the data
bus. Typically the power line is separated from the data line, although it is possible
to have a power line and the data line combined in a single line.
[0034] When multiple detection elements are interconnected, electrical fluctuations or an
electrical state of the power line(s) caused by the interconnection may be measured.
The measurement results can be characteristic of for example a position of the detection
element in a series of interconnected detection elements.
[0035] In an embodiment the detection element comprises a first power line, wherein the
measuring comprises detecting a voltage drop over a resistor in the first power line.
[0036] The first power line may be used for determining for example a position of the detection
element in a series of interconnected detection elements. The power on the first power
line may fluctuate or be different between detection elements.
[0037] In an embodiment the detection element further comprises a second power line. The
microcontroller can be configured to receive substantially a fixed power via the second
power line for powering the detection element. The detection element can be part of
an array of serially connected detection elements that are interconnected via the
data bus. The microcontroller can be configured to determine a number of detection
elements in the array based on the voltage drop and the voltage of the fixed power.
[0038] The second power line may be used to provide a fixed power to the electronics of
the detection element. When detection elements are interconnected, the power on the
second power line is substantially the same for all detection elements. The voltage
drop on the first power line can be related to the power on the second power line
to determine how many detection elements are interconnected by the data bus. This
may for example be achieved by a resistance on the first power line in the detection
element, causing the power to drop on the first power line with each detection element
in a series of detection elements. The number of detection elements is for example
determined by dividing the fixed power on the second power line by the amount of power
drop caused by the resistance on the first power line.
[0039] In an embodiment the detection element is placed in a protective casing to form one
of a sports timing detection mat, a vertically oriented sports timing detection element
and an overhead sports timing detection element.
[0040] In this configuration the detection element is particularly suitable for outdoor
use. The detection element may thus be protected from weather conditions and from
damage by contact with participants (e.g. by stepping on the detection element when
placed on the ground at a start line or finish line). Detection mats may be interconnectable
by interconnecting the protective casings, thus preventing the detection mats to separate.
Furthermore or alternatively the data busses, including the power lines if available,
of the detection elements are typically interconnectable by a socket-and-plug type
of connection, possibly with a socket being provided in the protective casing. When
interconnected, the detection elements in their protective casings may be connected
such that no open space exists between the detection elements. Alternatively a small
space may be present, in which case a (serial) cable connects the data busses of the
detection elements in their protective casings.
[0041] According to a second aspect of the invention an array of two or more sports timing
detection elements is proposed. The detection elements comprise the features as defined
in one or more of the embodiments above (either from the first aspect or the alternative
aspect of the invention). Two detection elements can be connected via the data bus.
The data busses together preferably form a serial data bus.
[0042] Thus, multiple detection elements are easily interconnectable to increase the detection
width of the detection elements, for example to cover the width of a track at a start
line or finish line.
[0043] In an embodiment a detection element is configured to switch off the transmitter
circuitry of said detection element based on a signal received from another detection
element.
[0044] When detection elements are part of an array, for example adjacent detection elements
may thus reduce interference by having one of the adjacent detection elements (possibly
temporarily) switching off the transmitter circuitry. The signal may be transmitted
via the data bus. Alternatively the signal is transmitted wirelessly between the detection
elements using any suitable transmission protocol (e.g. based on RFID, Bluetooth or
NFC). In the latter alternative the detection element typically includes a further
transmitter and receiver circuitry for implementing the wireless communication between
the detection elements.
[0045] According to a third aspect of the invention a sports timing detection system is
proposed. The sports timing detection system comprises the array of sports timing
detection elements as defined in one or more of the embodiments above. The detection
system further comprises the controller device connected to one of the detection elements
in the array via the data bus of the one of the detection elements.
[0046] Thus, a sports timing detection system may be realized, including interconnecting
detection elements forming an array of detection elements and including an external
controller device for collecting e.g. the sports timing data obtained by the detection
elements. The controller device is typically located at the side of a track and connects
to one of the detection elements in the array via the data bus.
[0047] In an embodiment the controller device is configured to switch on or switch off one
or more detection elements in the array.
[0048] Thus, in case of for example an expected or detected interference between two detection
elements, the controller device may switch on or off a detection element (or a transmitter
circuitry in the detection element). The data bus may be used to send a signal with
instructions to the detection element that is to be switched on or off.
[0049] In an embodiment the controller device is configured to set the transmission frequency
of the carrier signal of one or more of the detection elements in the array.
[0050] This enables for example two adjacent detection elements to use different frequencies
for transmitting the carrier signal (consequently resulting in different frequencies
for the corresponding backscatter signal). This may reduce or eliminate an expected
or detected interference between two detection elements. The data bus may be used
to send a signal with instructions to the detection element to use a particular carrier
frequency.
[0051] In an embodiment the detection system further comprising a power supply for providing
power to the array via the data bus, wherein the power supply is a part of the controller
device or otherwise externally connected, or a part of one or more of the sports timing
detection elements in the array.
[0052] This enables the detection system to include the power source for powering the electronics
of the detection elements in the array. With the power being provided via the data
bus, typically via one or more power lines in the data bus, only one of the detection
elements in the array needs to be physically connected to the power supply.
[0053] Hereinafter, embodiments of the invention will be described in further detail. It
should be appreciated, however, that these embodiments may not be construed as limiting
the scope of protection for the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] Aspects of the invention will be explained in greater detail by reference to the
drawings, in which:
Fig.1 shows a sports timing detection system of an exemplary embodiment of the invention;
Fig.2 shows different exemplary orientations of a detection element of an exemplary
embodiment of the invention;
Fig.3 and Fig.4 show detection elements of exemplary embodiments of the invention;
Fig.5 shows a cross-over switch part of a detection element of an exemplary embodiment
of the invention;
Fig.6 shows a polarization switch of an exemplary embodiment of the invention; and
Fig.7 shows a prior art sports timing detection system.
DETAILED DESCRIPTION
[0055] The sports timing detection element of the present invention may be used in sporting
events such as bicycle races, marathons and triathlons. Fig.1 shows an exemplary embodiment
wherein the detection element 21,23,25 is implemented as a detection mat placed on
the ground. As a single detection mat typically has a limited width, e.g. a width
of 1 meter, multiple detection mats are typically placed in one or two parallel lines
across the width of the track forming an array of detection elements. In Fig.1 three
detection mats are shown as an example. Any other number of detection elements or
detection mats may be used instead. Each detection element 21,23,25, may be provided
with a processor 22,24,26 for controlling a carrier signal 2 and processing a backscatter
signal 3 received in response from a tag 1 of a participant. The corresponding antenna
or antennas are not shown in Fig.1. Effectively, each detection element 21,23,25 has
embedded RFID reader functionality. The detection elements 21,23,25 are interconnected
by a data bus 27 for exchanging data, e.g. between the processors 22,24,26 and/or
with an external controller device 20. The external controller device 20 may be used
for storing data transmitted from the detection elements 21,23,25 via the data bus
27.
[0056] The timing system shown in Fig.1 includes a bib-tag assembly 1 and one or more detection
antennas (not shown) in one or more detection elements 21,23,25 that may be configured
as an elongated antenna mat placed on the ground, in the path of travel of the athletes
wearing the bib-tags. The antenna mat typically comprises one or more antennas configured
to pick up signals transmitted by the bib-tag assembly 1. The tag 1 may be configured
as a passive backscatter system wherein the tag 1 transmits a modulated tag signal
as a backscatter signal 3 to the detection antenna in a detection element 21,23,25
in response to a modulated trigger signal in a carrier signal 2 from the antenna mat.
If a participant wearing the bib-tag assembly 1 comes in the vicinity of the detection
antenna, the tag antenna may receive the modulated trigger signal 2 from the detection
antenna mat, which is used to power-up a processor in the tag 1. The detection antenna
mat typically transmits the modulated trigger signal 2 in a direction opposite to
the direction in which the athlete wearing the bib-tag 1 is moving. In response to
the modulated trigger signal 2, the tag transmits information stored in the processor
back to the detection antenna on the basis of a modulating back-scattered signal 3.
This way, the tag 1 may start sending out messages including e.g. a unique ID identifying
the bib. The detection antenna may pick the transmitted messages and transfer them
to the processor 22,24,26 in the detection element 21,23,25 for executing an algorithm
for determining a time associated with the tag on the basis of time of detection and
the signal strength of the received messages. The processed data may be subsequently
put on the data bus 27 and e.g. stored in a storage, e.g. a database, in the controller
device 20 connected to the data bus 27.
[0057] Because the backscatter signal is processed locally in the detection element 21,23,25
by the embedded processor 22,24,26, a remote RFID reader, such as RFID reader 10 in
Fig.7, need not be used and the antennas in the detection elements need not each be
connected to the remote RFID reader 10 via coax lines 14,15,16, such as shown in Fig.7.
The processor 22,24,26 locally processes the backscatter signal 3 and the thereby
obtained sports timing data, possibly including identification data of the participant
and timing information, may be provided to the data bus 27. Any device connected to
the data bus 27 may use the data for whatever purpose, such as the external controller
device 20 for storing the data or another detection element in the array of detection
elements.
[0058] The number of detection elements in the array is virtually unlimited, as there are
e.g. no coax cables to install in cable ducts as in Fig.7. Each detection element
may simply be connected to another detection element.
[0059] The use of the detection elements is not limited to the detection mats as shown in
Fig.1. The detection elements may be positioned in different orientations. Fig.2 shows
three exemplary orientations. Detection element 21 may be placed in a protected casing
to form a detection mat. A detection mat may be advantageous when the tag 1 is located
closer to and/or in an orientation towards the ground, such as when worn on the ankle
or at the wrist. Detection element 28 may be placed in a protective casing to form
a vertically oriented sports timing detection element. A vertically oriented detection
element may be advantageous when the tag 1 is located closer to and/or in an orientation
towards a side of the track, such as when worn on the wrist. Furthermore, a vertically
orientation keeps the track free of obstacles (i.e. detection mats on the ground form
small bumps), which is preferable in sporting events such as skiing or cycling. Detection
element 29 may be placed in a protective casing to form an overhead sports timing
detection element. An overhead detection element may be advantageous when the tag
1 is located higher on the participant and/or in an upwards orientation, such as when
worn on the upper arm.
[0060] The detection elements 21,28,29 of Fig.2 each contain a data bus and local processor,
such as shown in Fig.1. Similar to the example of Fig.1, two or more detection elements
21, two or more detection elements 28 and/or two or more detection elements 29 may
be interconnected via the data bus and possibly to an external controller device.
[0061] Two or more detection elements, e.g. when placed in protective casings such as shown
in Fig.2, are typically interconnected such that they form a straight line in a single
plane. It is possible that the interconnected detection elements follow a different
geometrical shape. For example, two (or more) detection elements may be connectable
at an angle within a plane, resulting in e.g. a zigzag shaped array of detection elements
on the ground. In another example two (or more) detection elements may be connectable
at an angle in different planes, resulting in e.g. a three-dimensional zigzag shaped
array of vertical detection elements at the side of a track. The protective casing
is not necessarily rectangular, such as shown in Fig.2, but may have any shape such
as a curved or irregular shape. It is possible that the data bus of two or more detection
elements are interconnected via a cable allowing a gap in between detection elements
and its protective casings.
[0062] Fig.3 shows a detection element 100 of an exemplary embodiment of the invention.
Detection element 100 may be used as detection element 21, 23, 25, 28 or 29 as shown
in Fig.1 and Fig.2. One or more antennas 101 are connected to a transmitter circuitry
104 for transmitting a carrier signal, such as a carrier signal 2 shown in Fig.1 or
Fig.2. The antenna 101 is further connected to a receiver circuitry 103 for receiving
a backscatter signal, such as a backscatter signal 3 shown in Fig.1 or Fig.2, in response
to the carrier signal. The signals are typically RFID signals. A microprocessor 105,
e.g. in the form of a processor running a computer program stored in a memory (e.g.
NVRAM or ROM) or a Field Programmable Gate Array (FPGA) that is hardcoded with the
computer program code, may control the transmitter circuitry 104 and receiver circuitry
103 and processed the received backscatter signal. Sports timing data thus obtained
by the microprocessor 105 may be put on a data bus 108. Connectors 113,114 enable
the data bus 108 of detection element 100 to be connected to the data bus of another
detection element or any other device having a connectable data bus.
[0063] Fig.4 shows a detection element 200 of another exemplary embodiment of the invention.
Detection element 200 may be used as detection element 21, 23, 25, 28 or 29 as shown
in Fig.1 and Fig.2. A first antenna 201 and a second antenna 202 are connected to
a first cross-over switch 206 and a second cross-over switch 207. The antennas 201,202
may be similar to the antennas 101,102 of Fig.3. The first cross-over switch 206 is
connected to a transmitter circuitry 204. The second cross-over switch 207 is connected
to a receiver circuitry 203. The transmitter circuitry 204 and the receiver circuitry
203 may be similar to the transmitter circuitry 104 and the receiver circuitry 103
of Fig.3. The cross-over switches 206,207 may be controlled by a microprocessor 205,
as depicted by the dashed lines. The microprocessor 205 may be similar to the microprocessor
105 of Fig.3. A microcontroller 215 controls data exchange between a data bus 208
and the microprocessor 205. It is possible that the microcontroller 215 and microprocessor
205 are integrated into a single microcontroller. A local clock 216 provides clock
pulses to the microcontroller 215 and possibly to the microprocessor 205. The data
bus 208, e.g. in the form of a CAN bus or RS485 bus, may comprise a data line 209
for exchanging data on the data bus 208. The data bus 208 may further comprise or
be extended with a power line 210 for providing preferably fixed power to the detection
elements connected to the data bus 208. The data bus 208 may further comprise a second
power line 211 for providing a variable power to the detection elements connected
to the data bus 208. The voltage on the second power line 211 may be varied by a resistor
212 in the second power line 211 or by any other means. The variable power on the
power line 211 may be used to identify the detection element in an array of connected
detection elements, as will be explained. Conceptionally, a directional coupler 217
may be installed in between the first cross-over switch 206 and the transmitter circuitry
204 and may be connected to a signal comparator 219, possibly via a logarithmic amplifier
218. The comparator 219 may be connected to the microprocessor 205 for processing
the output of the comparator 219.
[0064] With two antennas in the detection element 200, typically one antenna, in this example
antenna 202, operates as a transmit antenna and the other antenna, in this example
antenna 201, operates as a receive antenna. By controlling the cross-over switches
206,207 the transmitting/receiving function of the antennas may be switched, both
antennas may operate as transmit antennas or both antennas may operate as receive
antennas. Separating the receiving and transmitting in separate antennas advantageously
minimizes interference between the transmitted signal and the received signal before
processing in the microprocessor 205. As a result, receiver sensitivity may be increased.
Switching the transmitter/receiving function may be advantageous when e.g. a detuning
on the transmitter antenna is detected. Detuning may e.g. occur if a participant steps
on the transmitter antenna in the detection mat. In case of detuning the other antenna
may be used as transmitter antenna. This may be important as the carrier signal 2
is needed for powering the tag 1. To the reception of the backscatter signal 3 the
detuning has a lower impact.
[0065] Fig.5 shows an alternative cross-over switch configuration for use in a detection
element, such as detection element 200. Antennas 201 and 202, transmitter circuitry
204 and receiver circuitry 203 are similar to those shown in Fig.4. Furthermore, Fig.5
shows a directional coupler 217a, a first cross-over switch 206a and a second cross-over
switch 207a. Resistors 220, which are e.g. 50 ohm resistors, connect the directional
coupler 217 and the second cross-over switch 207a to ground. The first cross-over
switch 206a is used to select either the first antenna 201 or the second antenna 202.
The second cross-over switch 207a receives the backscatter signal via the transmit
antenna or via the other antenna. In a detection element having only one antenna,
the cross-over switches are typically set to receive the backscatter signal via the
transmit antenna. In a detection element having two antennas, the function of the
antennas may be switched, as explained above.
[0066] The microprocessor 205 may be configured to control the output power of the carrier
signal, e.g. to lower the power to a safe value or even to zero (i.e. turning off
the transmitter) in case of interference or (possibly severe) detuning of the transmitter
antenna.
[0067] The data bus 208 may be used to exchange data between microprocessors of different
detection elements 200 connected to the data bus 208. The data bus 208 may be used
to exchange data to a controller device 20 connected to the data bus 208. The controller
device 20 may collect registration data as obtained by the microprocessors 205 in
the detection elements 200. The collected registration data may be stored in the controller
device 20 or forwarded from the controller device 20 to another server via any data
communication means.
[0068] The controller device 20 may be used to synchronize the detection elements. Hereto
control data may be transmitted from the controller device 20 to the detection devices
via the data bus. Synchronizing may result in two neighboring detection elements alternating
the on/off state of the transmitter antenna or two neighboring detection elements
using different transmitting frequencies for the carrier signal. This may avoid two
detection elements serving a single tag and processing its backscatter signal. Alternatively
or additionally the microprocessor 205 may be configured to synchronize the detection
element 200 with one or more neighboring detection elements.
[0069] The directional coupler 217 may be used to detect a reflection signal. For example
due to an antenna mismatch, a reflection of the carrier signal 2 may be detected on
the antenna ports 201,202. This reflection is called the reflection signal. The comparator
219 may be used to determine if the reflection signal is larger at one of the two
antennas. The comparison result may then be used by the microprocessor 205 to switch
off the antenna with the highest reflection signal. If the power of the reflection
signal is too large, the backscatter signal 3 may not be detectable. Disabling the
transmission antenna or lowering the transmission power for transmitting the carrier
signal 2 may reduce or eliminate the reflection signal, enabling the backscatter signal
3 to be detectable again. The disabling of the transmission antenna or lowering of
the transmission power may be a temporary measure. Alternatively the comparison result
may trigger the microprocessor 205 to switch the transmitting/receiving function of
the two antennas 201,202.
[0070] The fixed power line 210 and variable power line 211 may be used to determine a position
of the detection element in an array of detection elements and to determine the total
number of detection elements in the array. In the following example the fixed power
is set to 12V. The first detection element in the array is typically connected to
a power supply. Hereto the connector 213 of the first detection element may be connected
to the power supply such that the fixed power line 210 is connected to the 12V power
supply. Also the variable power line 211 may be connected to the 12V power supply
via the connector 213. All detection elements in the array are now effectively connected
to the 12V power supply via the fixed power line 210 in the data bus 208. The resistor
212 in each detection element 200 makes the voltage in the variable power line 211
drop. The last detection element in the array typically has a terminator connected
to the connector 214 to terminate the data bus 208. The terminator effectively grounds
the variable power line 211 to ground in the last detection element of the array.
[0071] In the example above the power supply is part of the controller device 20. Alternatively
a separate power supply may be used, the power supply may be part of one or more of
the detection elements, or the power supply may installed in the protective casing
of the detection element.
[0072] The microcontroller 215 may calculate the position of the detection element 200 by
performing the following calculation: position = V
1/(V
1-V
2). Herein, V
1 is the voltage on the variable power line 211 before the resistor 212, i.e. at the
side of connector 213, and V
2 is the voltage on the variable power line 211 after the resistor 212, i.e. at the
side to connector 214.
[0073] The microcontroller 215 may calculate the total number of detection elements in the
array by performing the following calculation: number of detection elements = V
power/(V
1-V
2). Herein, V
power is the voltage on the fixed power line 210, V
1 is the voltage on the variable power line 211 before the resistor 212, i.e. at the
side of connector 213, and V
2 is the voltage on the variable power line 211 after the resistor 212, i.e. at the
side to connector 214.
[0074] Instead of using a fixed power line 210 in combination with a variable power line
211 and resistor 212, any other electrical means involving any electronic component
may be used for detecting fluctuations in one or more power lines and relating these
fluctuations to a position in the array and the total number of detection elements
in the array.
[0075] Fig.6 shows an antenna module 120 of an exemplary embodiment of the invention. The
antenna module 120 may be used as antenna 101, 201 and/or 202, as shown in the exemplary
figures 3, 4 and 5. The antenna module 120 may contain a ground plane with a patch
121 located thereon. Part of the antenna module 120 is a polarization switch 122 for
switching the polarization of the antenna module 120. The antenna module 120 is connected
to a part 125 of the detection element. Depending on the configuration the part 125
of the detection element may be receiver circuitry 103, transmitter circuitry 104,
receiver circuitry 203, transmitter circuitry 204, cross-over switch 206 or cross-over
switch 207, as shown in exemplary figures 3, 4 and 5. Other possible configurations
of the detection element are not excluded; the part 125 of the detection element may
be any other part of the detection element that may be connected to the antenna module
120. The polarization switch 122 is typically controlled by a microcontroller of the
detection element, such as microcontroller 105 or 205. In the example of Fig.6 the
polarization is switchable between a horizontal polarization and a vertical polarization
on patch ports 121a and 121b, respectively.
[0076] Instead of switching between a horizontal and vertical polarization the polarization
switch 122 may be configured to switch between other polarizations, such as between
linear and circular polarization.
[0077] As described above, the data bus may be implemented as a Controller Area Network
(CAN) bus. The CAN standard defines a communication network that links all the nodes
connected to a bus and enables them to talk with one another. There may or may not
be a central control node, and nodes may be added at any time, even while the network
is operating (hot-plugging). Unlike a traditional network such as USB or Ethernet,
CAN does not send large blocks of data point-to-point from node A to node B under
the supervision of a central bus master. In a CAN network, many short messages may
be broadcast to the entire network, which provides for data consistency in every node
of the system. The CAN communications protocol, ISO-11898: 2003, describes how information
is passed between devices on a network and conforms to the Open Systems Interconnection
(OSI) model that is defined in terms of layers.
[0078] The CAN communication protocol is a carrier-sense, multiple-access protocol with
collision detection and arbitration on message priority (CSMA/CD+AMP). CSMA means
that each node on a bus must wait for a prescribed period of inactivity before attempting
to send a message. CD+AMP means that collisions are resolved through a bit-wise arbitration,
based on a preprogrammed priority of each message in the identifier field of a message.
The higher priority identifier always wins bus access. That is, the last logic-high
in the identifier keeps on transmitting because it is the highest priority. Since
every node on a bus takes part in writing every bit "as it is being written," an arbitrating
node knows if it placed the logic-high bit on the bus. The ISO-11898:2003 Standard,
with a standard 11-bit identifier, provides for signaling rates from 125kbps to 1
Mbps. The standard was later amended with an "extended" 29-bit identifier. The standard
11-bit identifier field provides for 211, or 2048 different message identifiers, whereas
the extended 29-bit identifier provides for 229, or 537 million identifiers.
[0079] Bus access is typically event-driven and takes place randomly. If two nodes try to
occupy the bus simultaneously, access is implemented with a nondestructive, bit-wise
arbitration. Nondestructive means that the node winning arbitration just continues
on with the message, without the message being destroyed or corrupted by another node.
The allocation of priority to messages in the identifier is a feature of CAN that
makes it particularly attractive for use within a real-time control environment. The
lower the binary message identifier number, the higher its priority. An identifier
consisting entirely of zeros is the highest priority message on a network because
it holds the bus dominant the longest. Therefore, if two nodes begin to transmit simultaneously,
the node that sends a last identifier bit as a zero (dominant) while the other nodes
send a one (recessive) retains control of the CAN bus and goes on to complete its
message. A dominant bit typically overwrites a recessive bit on a CAN bus.
[0080] The robustness of CAN may be attributed in part to its abundant error-checking procedures.
The CAN protocol incorporates five methods of error checking: three at the message
level and two at the bit level. If a message fails any one of these error detection
methods, it is not accepted and an error frame is generated from the receiving node.
This forces the transmitting node to resend the message until it is received correctly.
However, if a faulty node hangs up a bus by continuously repeating an error, its transmit
capability is removed by its controller after an error limit is reached. Error checking
at the message level is enforced by CRC and ACK slots. The 16-bit CRC contains the
checksum of the preceding application data for error detection with a 15-bit checksum
and 1-bit delimiter. The ACK field is two bits long and consists of the acknowledge
bit and an acknowledge delimiter bit. Also at the message level there can be a form
check. This check looks for fields in the message which must always be recessive bits.
If a dominant bit is detected, an error is generated. The bits checked are the SOF,
EOF, ACK delimiter, and the CRC delimiter bits. At the bit level, each bit transmitted
is monitored by the transmitter of the message. If a data bit (not arbitration bit)
is written onto the bus and its opposite is read, an error is generated. The only
exceptions to this are with the message identifier field which is used for arbitration,
and the acknowledge slot which requires a recessive bit to be overwritten by a dominant
bit. The final method of error detection is with the bit-stuffing rule where after
five consecutive bits of the same logic level, if the next bit is not a complement,
an error is generated. Stuffing ensures that rising edges are available for on-going
synchronization of the network. Stuffing also ensures that a stream of bits are not
mistaken for an error frame, or the seven-bit interframe space that signifies the
end of a message. Stuffed bits are removed by a receiving node's controller before
the data is forwarded to the application. With this logic, an active error frame consists
of six dominant bits-violating the bit stuffing rule. This is interpreted as an error
by all of the CAN nodes which then generate their own error frame. This means that
an error frame can be from the original six bits to twelve bits long with all the
replies. This error frame is then followed by a delimiter field of eight recessive
bits and a bus idle period before the corrupted message is retransmitted. It is important
to note that the retransmitted message still has to contend for arbitration on the
bus.
[0081] One embodiment of the invention may be implemented as a program product for use with
a computer system. The program(s) of the program product define functions of the embodiments
(including the methods described herein) and can be contained on a variety of computer-readable
storage media. Illustrative computer-readable storage media include, but are not limited
to: (i) non-writable storage media (e.g., read-only memory devices within a computer
such as CD-ROM disks readable by a CD-ROM drive, ROM chips or any type of solid-state
non-volatile semiconductor memory) on which information is permanently stored; and
(ii) writable storage media (e.g., floppy disks within a diskette drive or hard-disk
drive or any type of solid-state random-access semiconductor memory or flash memory)
on which alterable information is stored. Moreover, the invention is not limited to
the embodiments described above, which may be varied within the scope of the accompanying
claims.
1. A sports timing detection element based on backscattering modulation, preferably RFID
backscattering modulation in the UHF band, the detection element comprising at least
one antenna, a receiver circuitry, a transmitter circuitry and a microprocessor, wherein
the microprocessor is configured to:
activate the transmitter circuitry for transmitting a carrier signal via the at least
one antenna; and
process a backscatter signal received via the at least one antenna and the receiver
circuitry in response to the carrier signal,
the detection element further comprising a data bus for exchanging data with a further
detection element.
2. The detection element according to claim 1, further comprising a polarization switch
to switch the polarization of an antenna, such as between a horizontal polarization
and a vertical polarization or between a linear and a circular polarization.
3. The detection element according to claim 1 or 2, comprising a first antenna and a
second antenna, wherein the detection element is configured to transmit the carrier
signal via the first antenna and to receive the backscatter signal via the second
antenna.
4. The detection element according to claim 3, further comprising a cross-over switch
to switch between the first antenna and the second antenna for transmitting the carrier
signal.
5. The detection element according to claim 3 or 4, wherein the detection element is
configured to receive the backscatter signal via the first antenna and the second
antenna.
6. The detection element according to any one of the claims 3-5, further comprising a
comparator module configured to with a second reflection signal received via the second
antenna to obtain a comparison result, and wherein the microprocessor is further configured
to, based on the comparison result,
switch off one of the first antenna and the second antenna for transmitting the carrier
signal, or
lower a transmission power for transmitting the carrier signal via one of the first
antenna and the second antenna.
7. The detection element according to any one of the preceding claims, further comprising
a microcontroller that is configured to determine an identity of the detection element.
8. The detection element according to claim 7, wherein the data bus comprises one or
more power lines, and wherein the microcontroller is configured to determine the identity
based on a measurement result obtained by measuring the one or more power lines.
9. The detection element according to claim 8 comprising a first power line, wherein
the measuring comprises detecting a voltage drop over a resistor in the first power
line.
10. The detection element according to claim 9 further comprising a second power line,
wherein the microcontroller is configured to receive substantially a fixed power via
the second power line for powering the detection element, and wherein, when the detection
element is part of an array of serially connected detection elements that are interconnected
via the data bus, the microcontroller is configured to determine a number of detection
elements in the array based on the voltage drop and the voltage of the fixed power.
11. The detection element according to any one of the preceding claims, wherein the detection
element is placed in a protective casing to form one of a sports timing detection
mat, a vertically oriented sports timing detection element and an overhead sports
timing detection element.
12. An array of two or more sports timing detection elements according to any one of the
claims 1-11, wherein two detection elements are connected via the data bus, and wherein
the data busses together preferably form a serial data bus.
13. The array according to claim 12, wherein a detection element is configured to switch
off the transmitter circuitry of said detection element based on a signal received
from another detection element.
14. A sports timing detection system comprising the array of sports timing detection elements
according to claim 12 or 13, and comprising the controller device connected to one
of the detection elements in the array via the data bus of the one of the detection
elements.
15. The detection system according to claim 14,
wherein the controller device is configured to switch on or switch off one or more
detection elements in the array.
16. The detection system according to claim 14 or 15, wherein the controller device is
configured to set the transmission frequency of the carrier signal of one or more
of the detection elements in the array.
17. The detection system according to any one of the claims 14-16, further comprising
a power supply for providing power to the array via the data bus, wherein the power
supply is a part of the controller device or a part of one or more of the sports timing
detection elements in the array.